Prepare a canning pot water bath and four half-pint jars.

Place the pears in a large nonreactive skillet. Stir in the sugar. Let sit, stirring once or twice, until the sugar begins to dissolve, 5 to 10 minutes.

Bring the mixture to a boil over high heat. Reduce the heat to medium high, and cook, stirring regularly, until the pears start to break down and the liquid begins to evaporate, 8 to 10 minutes. Stir in the lemon juice and cardamom. If you find that the chunks of fruit are too big for your liking, use a potato masher to help break them down.

Continue to cook until the jam has thickened, 2 to 3 minutes more; it is done when you can pull a spatula through the jam and the space you clear stays open for 2 or 3 seconds. The mixture will continue to thicken as it cools, so make sure to stop a little shy of your desired thickness.

Use a funnel to pour the jam into the prepared jars, leaving 1/2-inch headspace. Wipe the rims, apply the lids and rings, and process in a boiling water bath canner for 10 minutes.

Remove the jars, and put them on a folded kitchen towel to cool. When the jars have cooled enough that you can comfortably handle them, check the seals. Sealed jars can be stored at room temperature for up to a year. Any unsealed jars should be refrigerated and used promptly.